Local effects of silica on tumor growth inhibition. A histological study

The subcutaneous implant of a fibrosarcoma covered with silica, in rats, resulted in a temporary retardation of tumor growth. The histological study demonstrated that the silica provoked, within and at the periphery of the tumor, inflammatory foci which altered the composition of the fundamental substance and which promoted the accumulation of principally macrophages in the interior as well as on the surface of the tumoral mass. Besides the macrophages of the host, a number of tumor cells do also phagocyte silica crystals, leading to destruction of all those cells. The authors are of the opinion that the local modifications provoked by silica, could have interfered in the adaptation of the tumor with its nutrient stroma. Of these modifications, the stroma sclerosis seems to be the most effective in the inhibition of tumor growth. Some correlations were suggested between the here described results and those obtained by other workers who have used other inflammatory agents of different nature.